.header{
    background-position: no-repeat center center;
    background-image: url('../image/bg1.jpg');
    background-size: 100% 100%;
    position: absolute;
    width: 100%;
    height: 100%;
    overflow: hidden;
}
#site-logo{
    margin-top:5%;
}
#img-logo{
    height:200px;
    width:400px;
}
#nav{
    float:right;
    margin-top: 100px;
}